The present disclosure relates to a wireless power receiver, and more particularly, to a wireless power receiver for wirelessly receiving power from a wireless power transmitter.
A mobile terminal such as a mobile phone or a personal digital assistant (PDA) is generally powered by a rechargeable battery. In order to charge such a rechargeable battery, electrical energy is supplied to the rechargeable battery via a separate charging device. Typically, the charging device is electrically connected to the rechargeable battery via contact terminals formed on the charging device and the rechargeable battery.
However, in contact-type charging scheme, the contact terminals may be contaminated by foreign substances, causing unstable battery charging. Further, battery charging may not be performed correctly if the contact terminals are exposed to the moisture.
Thus, non-contact or wireless charging technology has been recently developed and used for many electronic devices.
For example, wireless power transmission/reception-based systems may use wireless charging technology for wireless charging. An exemplary wireless power transmission/reception-based system may be a mobile phone whose battery may be wirelessly charged when a user places the mobile phone on a charging pad, instead of connecting an external charging connector to the mobile phone. Wireless electric toothbrushes or cordless electric shavers are also generally known as wireless charging technology-based devices. Generally, wireless charging technology may improve the waterproof capability of an electronic device because the electronic device may be wirelessly charged with minimum or no exposure of its components. Wireless charging technology may also improve the portability of an electronic device when wired charging becomes optional. Wireless charging technology may also evolve significantly in the coming electric car era.
Wireless charging technology may be roughly classified into an electromagnetic induction power transmission scheme based on coils, a resonance power transmission scheme based on resonance, and a radio wave radiation (or radio frequency (RF)/microwave radiation) power transmission scheme that converts electrical energy into microwaves.
Electromagnetic induction-based power transmission scheme is generally based on transmitting power between a primary coil and a secondary coil. If a magnet is moved around a coil, a current may be induced. Based on this principle, if a magnetic field is generated at a transmitter, a current may be induced due to a change in the magnetic field at a receiver, producing the energy. This phenomenon is called magnetic induction, and a magnetic induction-based power transmission scheme is efficient in energy transmission.
As for the resonance power transmission scheme, Professor Soljacic and a research team at Massachusetts Institute of Technology (MIT) announced in 2005 a wireless charging system in which power is wirelessly transmitted to an electronic device even though the electronic device is a few meters away from a charging device, by using resonant power transmission principle as coupled mode theory. The wireless charging system proposed by the MIT team uses resonance, in which, for example, if a tuning fork rings, a nearby wineglass also rings at the same frequency. The research team generates electromagnetic waves containing electrical energy resonating at a resonant frequency, instead of resonating sounds. The resonated electrical energy is directly transmitted when an electronic device having a resonant frequency is nearby. The unused electrical energy is re-absorbed as an electromagnetic field. Unlike other electromagnetic waves, the resonated electrical energy does not seem to affect machines or humans nearby.
The electromagnetic induction-based power transmission/reception scheme may be different from the resonance-based power transmission/reception scheme. For example, the electromagnetic induction-based power transmission/reception scheme and the resonance-based power transmission/reception scheme may be different in terms of their wireless power transmission/reception frequencies, and in terms of values of respective circuit elements. For example, a wireless power receiver designed for the resonance-based power transmission/reception scheme may not receive wireless power where an induction scheme-based wireless power transmitter is disposed. Conversely, a wireless power receiver designed for the induction scheme may not receive wireless power where a resonance scheme-based wireless power transmitter is disposed.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.